It cannot safely be ignored (6,6)
I believe the answer is:
danger signal
'ignored' is the definition.
Both the definition and answer are adjectives.
Perhaps they are linked in a way I don't understand?
I cannot understand how the rest of the clue works.
Can you help me to learn more?
(Other definitions for danger signal that I've seen before include "Red light" , "Red flag, for example" , "Warning of hazard" .)